It is now common practice to use a tool, such as a numerically controlled laser or the like for cut out pieces of given shape from sheet or plate material, e.g. an animal hide. It is also known to store a cutting out plan in a computer memory suitable for making best use of the sheet or plate. Such an optimal cutting out plan may be calculated by computer means providing the said sheet or plate is regular in shape, e.g. when it is made of synthetic material. The computer with the stored optimal cutting out plan can then control displacements of a laser as a function of the plan. A special problem arises when the material to be cut up is leather. Hide is not as easy to use as a plate or sheet of uniform manufactured material whose shape is predetermined prior to manufacture as a function of the use for which it is intended. No two hides are the same shape, their outlines always differ to some extent, they may include defects, they have a grain direction, etc. Taking the footwear industry as an example, all these peculiarities are taken into account when determining an optimum cut out plan. Templates corresponding to different footwear parts, in different sizes and in different designs are placed manually on each hide by specialists. The resulting cut out plan is thus specific to each hide, and the business of placing templates on a hide must be started afresh for each hide. It then becomes necessary to detect each individual cut out plan, i.e. to recognize the templates and to locate their positions on the hide, so that the plan can be stored in a computer memory. The computer can then control cut out or perform some other process, e.g. calculate wastage, control some other operation, make modifications, etc.
Proposals have already been made for identifying templates by means of bar codes. However, this type of marking is not easily read by a camera, furthermore the code must be read along a fairly accurately determined direction. Unfortunately, templates are placed in completely random directions on a hide. It thus becomes very complicated to read and record the bar codes of such templates.